1. Field of the Invention
The invention relates generally to volumetric analysis of a component of a cryogenic liquid, in particular, to a system for determining the percent by volume of liquid nitrogen in a stored quantity of liquified natural gas (LNG) whose composition of liquified hydrocarbon gases is known, and which is stored at atmospheric pressure.
2. Description of the Prior Art
At the present time, the only method which is used to determine the amount of nitrogen present in a quantity of liquified natural gas is that of taking a sample and analyzing it for all of the liquid components. This procedure is time consuming and subject to error, especially since the nitrogen present in the liquified natural gas normally constitutes only a small percentage of the total quantity of the liquid.
It is desirable to know the nitrogen content of stored liquified natural gas because such nitrogen is an inert component of the liquid, with no heating value; consequently, any nitrogen present has a deleterious effect on the heating value of the liquid, upon which the monetary value of the liquified natural gas is based. Also, continuous monitoring of the LNG nitrogen content is desirable, since nitrogen is more volatile than the LNG hydrocarbon components, and will boil off during storage. In addition, the measured nitrogen content can be used with LNG density measuring equipment to correct for minor density-dielectric constant variations in a LNG mixture.